Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$62.80	7.839%	$67.7229	$67.72	$67.70	$67.70
Purchase #2	$27.45	7.462%	$29.4983	$29.50	$29.50	$29.50
Purchase #3	$227.83	11.829%	$254.78	$254.78	$254.80	$254.80
Purchase #4	$160.72	7.575%	$172.8945	$172.89	$172.90	$172.90
Purchase #5	$124.52	7.835%	$134.2761	$134.28	$134.30	$134.30
Purchase #6	$140.59	7.104%	$150.5775	$150.58	$150.60	$150.60
Purchase #7	$135.43	10.788%	$150.0402	$150.04	$150.05	$150.00
7 purchase totals =	$879.34		$959.7895	$959.79	$959.85	$959.80